This invention provides apparatus and method for re-sealing a toner hopper that is a part of a toner cartridge used in a dry toner printer or photocopying machine.
Recent developments in the electrostatic printing industry have led to the introduction of dry toner cartridges for use in relatively low cost computer printers and photocopying machines. These cartridges are intended by their manufacturers to be disposable, but have a sufficiently high replacement cost that a "recharging" industry has grown to provide reloaded and rebuilt cartridges. Thus, a nominally disposable cartridge may, during its service life, be recharged with new toner material multiple times.
It is customary for the original manufacturer of a printer or copying machine cartridge to fill the toner hopper with toner prior to completing the assembly of the unit and to seal the filled toner hopper with a plastic sheet that is suitably secured (e.g. by welding) to a flange at the top of the toner hopper. The sealed toner hopper is then assembled with the balance of the toner cartridge elements (e.g. by welding the two longer of the four edges of the flange at the top of the toner hopper to a mating flange on a roller housing subassembly), thereby forming a channel wherein lies the plastic sealing sheet. The user, immediately before installing the cartridge, grasps a tab portion of the plastic sealing sheet and pulls the sheet out of the channel, thereby opening the hopper and allowing toner to be metered out of the hopper onto a receiving surface.
Several earlier inventors have sought to provide method and apparatus for sealing the toner hopper from the balance of the toner cartridge during a recharging operation. Absent such a seal, toner is almost invariably spilled from the cartridge when the recharged cartridge is shipped. Notable among the prior art is the teaching of Woolley in U.S. Pat. No. 4,862,210, which is primarily directed toward toner cartridges made by the Canon Corporation. Woolley's replacement seal is made by partially disassembling a toner cartridge that is to be recharged for the first time, fastening brackets in the channel that was initially occupied by the plastic sealing sheet so as to form an improved channel of well-defined geometry, and then inserting a generally rigid sealing member into the improved channel. During subsequent recharging operations the toner cartridge does not need to be partially disassembled, as a seal can be inserted into the improved channel through a slot at one end of the toner cartridge. The disclosure of Woolley is herein incorporated by reference.
Patterson, in U.S. Pat. No. 4,930,684, teaches a closure strip and method for remanufacturing a toner cartridge of the same sort as was addressed by Woolley. The closure strip of Patterson includes a firm substrate member of a width slightly less than the distance between the walls of the channels running the length of the toner cartridge and a length somewhat longer than the toner cartridge so that a portion of the substrate sticks out through the slot in the end of the toner cartridge. Thus, the seal can be grasped and easily removed. A resilient sealing element is attached to one face of the substrate member and is intended to fit snugly between the hopper flange and the roller housing subassembly flange portions of the interior channels that were formed in the cartridge during its original manufacture. It has been found that Patterson's seal is difficult to insert in the narrow slots that are present in the ends of commercially available cartridges, because the resilient element of the seal tends to hang up on the edges of the slot. If the resilient material is torn by the edges of the slot, it provides a less than totally effective seal. The disclosure of Patterson is herein incorporated by reference.
Another prior art approach to providing a toner cartridge seal during recharging involves disassembling the cartridge, cleaning both flanges, and securing a plastic sheet over the toner hopper--i.e. duplicating the sealing method used by the original manufacture. This approach, aside from the obvious difficulty posed by disassembly and reassembly of a welded structure, also requires extreme cleanliness, which may be relatively easy to provide in a factory that is handling virgin materials, but which is very difficult to provide in a recharging environment.
Yet another prior art sealing approach uses a rigid sealing sheet with a magnetized layer on one side thereof. Since the dry toner powder is ferromagnetic, this layer is supposed to keep enough toner attracted to the sheet to give the sheet an effective thickness large enough to seal the channel.